Screw-thread-cutting means for bench lathes



April 27,1926. 1,582,669

Y H. E. DURKEE SCREW THREAD CUTTING MEANS FOR BENCH LATHES Filed Feb. 5. 1923 5 Sheets-Sheet l NVE'NTR f April 27 1926. 1,582,669

H. E. DURKE-E SCREWTHREA'D CUTTING MEANS FOR BENCH LATHES Filed Feb. 5, 1925 s sheets-sheet 2 A `INI/ENTQR.

April 27 1926.

' H. E. DURKEE SCREW THREAD CUTTING MEANS FCR BENCH LATHES Filed Feb. 5. 1923 3 Sheets-Sheet 3 INVENTCR .7(5. 191 we-L ATTORNEYS.

Patented pr. 27, i926.

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HENRY E. D'U'RKEE, OF GLASTONBURY, CNNCTCUT, ASSIGNOB TO ERATT 6c ti/'HIT- NEY COMPANY, 0F NE'W YORK, N. Y., A CORPOBATON 0F NEW JERSEY. i

SCREW-THREAD-CUTTING MEANS'FOR BENCH LATHES.

Application filed February 5, 1923. Serial No. 617,037.

To all wher/tet may concern:

lie itltiiown that l, HENRY citizen of the United States, residing at Glastonbury, in the county of llafttoiily and State of Connecticut, have invented certain new and useful Improvements in Screw- Thread-Cutting Means for Bench Lathes, of which the following is a specification.

VThis invention relates to lathes and in particular to an improved form of screw thread cutting device adapted to be used in connection with a bench type of lathe.

V'An object of the present invention is to provide means enabling screw'threads tovbe cut in a bench lathe at a high rate of speed, and without danger of the threads being mutilated by incorrect engagement ofthe follower controlling the longitudinal movements of the threading tool with the lead screw rotated from the work spindle at different speeds.

More particularly it is an object of the invention to provide means to properly engage thefollower with the lead screw so that with successive cutting operations. of the tool, the follower will be in engagement with the saine convolution of the thread onthe lead screw and the toolv will successively-enn 'gage and progressively roim the screw,v

thread being cut.

One of the features of the invention which is advantageous is that screw threads having any leader pitch can be cut by means of a single lead screw-driven from the head- `stock spindler through appropriate geared change speed mechanism.

ln one of the modifications of the invention the lead screw,'through geared connections, rotates va dial provided with a plurality of graduations. The positions of the.

graduations on the dial relative to a fixed point adjacent the dial indicate eXactl;l when the follower carried by and movable with the tool carriage is to be manuali i engaged t: c) c:

with thethieads of the lead screw. 'ln the second modification of thel invention, the followeiis positively held out of engagement with thel threads of the lead screw until exactly the proper time for it to engage the lead screw, and,A at thatvtime only it is permitted to be oscillated into engagement therewith.

With these and other objects in view, my

invention consists in the features of con- E. Drinnen, a

struction and operaticn'set forth in the following specification and illustrated in the accompanying drawings.

y1n the accompanying drawings annexed hereto and forming a part of this specification, 1 have shown my invention embodied in a well known type of bench lathe, the drawings, however, are not to be construed as defining or limiting the scope of the inand its means of attachment` vto the lead screw.

Fig. t is a rear elevation similar to'Fig. 2 but showing a modified form of the present invention. V

Figlv is an end elevation of the form shown in Fig. il, parts being broken away to more clearly show their construction.

In the above mentioned drawings, l have shown several niodiiications of the invention which are now` deemed preferable but it will be understood that changes and modifications may be made within the scope of the appended claims without departing from the spirit of the invention.

Referring more particularly to the drawings,'niy invention in its broadest aspect-is adapted to be applied to a lathe having the following principal parts: first, a baseV 10 having work supporting andl rotating means 11, thatY shown being the usual vforni of work supporting and rotating spindle, and anoscillating tool holder 12 preferably mounted Y in the usual manner upon an oscillating and longitudinally moving shaft 13 in4 rear of the' base of the lathe. Also, the lathe has a lead screw 14textending parallel to the work supporting and rotating spindle 11 and adapted to be driven therefrom at any predeterminedratio thereto byv suitable change gearing 15. in addition, the oscillating .shaf '13, towhich the tool holder 12is tached, is also provided with anarm 15 haing a follower 1? adapted to engage the lead screw lll. All of the above parts are those usually found in bench lathes having screw thread cutting attachments and my `present invention relates to improvements adapted to be used directly in connection therewith.

These improvements comprise means rotated from the lead screw 1l and at a given fixed ratio thereto. These means in one modification are provided with indicia and in the otaer with spaced apertures, the purposes or' each ot which will be presently described. In both modilications, the oscillatin;- shaft 13 is provided with the member 17 adapted in its operative position to engage in said lead screw and thus cause the tool 1S and its carriage 12 to move axially7 and, in one modification this vl'ollower carrying arm 1G has a projection mounted thereon positioned adjacent the member rotated by the spindle 11.

lt is the usual practice in cutting screw threads in a bench lathe to oscillate the tool holding` traine 12 as by means ot a handle 12n in a manner to engage and disengage a tool 18 with the work A.. rlhis engagement and disengagement in usual practice takes place while the work is constantly rotating in one direction. By means ot the follower 17 on arm 16 attached to the shatt 13 which is engaged and disengaged with the lead screw7 141, oscillation ot this tool holder 12 gives the tool holder 12 an axial movement. This axial movement of the tool 12. which takes place while it is in engagement with and during' the rotation ot the work A, forms the screw thread. It has been found in practice that, when screw threads are being formed and while the work is being rapidly rotated. the threads may be mutilated by the incorrect engagement ot the follower 17 with the lead screw 11-. lt. will be undersood that it' the lead of the work being threaded is incommensurate with the lead ot' the lead screw. the Jfollower must engage a particular convolution ot the threads ot' the lead screw duringl each ot the successive cutting operations. To enable this to be done expeditiously and without stopping rotation ot the work A and lead screw 1l. I mount the mechanism 'forming the present invention upon and in position to be driven b v the lead screw.

ln both of the embodiments ot the present invention which have been illustrated. the lead of the screw 1dr is one-twelfth ot an inch and the worm wheel 20 driven there by is provided 4with forty-eight teeth. These may be widely varied. it being` essential merely that the number olE teeth on the worm wheel 2O should have a large number ot factors. ln the modilication shown in Fi; 1. 2 and 3 in which the worm wheel 20 is driven trom an extension ot the screw 1l. the lead ot the worm 11a on this extension corresponds exactly with the lead ot the main screw 1+i. lThe tool support 12 with its tool 18 will therefore be advanced tour inches with one complete rotation ot the worm wheel 20.

ln the modihcation et the invention illustrated in Figs. 1, 2 and 3, I provide a vcrtical shalt 21 preferably secured in a suitable honsiirs;` 21 which may be rigidly attached to the lathe bed 10. This vertical shaft 21 at its lower end is provided with the worin wheel 2O previously referred to, the teeth ot which are adapted to engage with the worm 1-1il `formed on the end ot the shait carrying` the lead screw 1l. This vorm 1l, as above stated, has the same lead as the lead screw 1l. lt. will be seen from this construction that rotation ot the work A and lead screw 1l will constantly rotate the worin vfhecl 2O and the vertical shalt 21 so that a dial 22 0r plate detachably fastened to the upper end o'f the shaft 21 is constantly rotated.

On this dial or plate are graduations 23. there beine` preferably four major graduations 2t and many individual graduations as there are teeth in the worm wheel. Adjacent the periphery oi" this dial 22 a projection 25 carrying a zero line 2G. This may be attached as shown to the housing,- 2111. vWhen it is desired to make use ot this mechanism, it is only necessary to observe the relative positions ot the indicia 2l on the dial 22 at the time the tollower 17 carried by the oscillating' shaft 123 is oscillaicd to its engaged position with the lead screw 14. This engagement in successive cuts upon the work A must take place while one of the major `Q'raduations` 2l is just passingl the zero line. This will assure the tool being engaged correctly in .proper relation lo the thread being` cnt as it will assure the lollower 17 engaging' the same convolution of the lead screw 1l at the start ot the thread. Under certain conditions as when the number ot threads being cut per inch is trac* tional as 11l/- 2l/Hi then the number ot major `efradnations` 23 on the dial must be. changed accordingly.

its the work usually done in bench lathes to which my invention is particularlv applicahle is ot small diameter and consequently rotates at high speed. it is ditlicult to properly engage the follower 17 with the lead screw 11 e.\:actl v :it a time when one of the major indicia 2l is passing the zero line 2G. l. therefore. in l and :7. show a moditied t'orm ot the invention which prevents any engagement oi; the 'follower 17 with the lead screw 1-l and consequently prevents the tool engagingi the work until proper relative positions of the parts occur.

ln this torni ot the invention. the lead screw 11 and its driving' means 'lroin the work spindle 11 as well as the oscillatingl snr-,tt 13 and attached parts are exactly the lli() same as in the vpreviously described form.

,The worm wheel 2O however may preferably `directly engage the lead screw 14 rather than carried thereby. llhis' shaft 31 has near onel end a worm wheel 20", which may have enactly the same number of teeth Vas worm wheel 20 but adapted to directly engage the screw threads of the lead screw 14. At the vopposite end of this rotating shaft 31 is a plateA 32 detacliably mounted thereon and `having a plurality of notches 33 therein,

which plate '32, it will be seen, is positively driven so long as the lead screw lli is rotating. j

Extending from'the oscillating arm 16 carrying the follower 17 .is a small linger member 34, the over-hanging end'of which lies adjacent the notched plate 32. This projection or finger 34 may be detachably secured, as shown, to one side of this arm 16. lt will be seen fromtheabove that when it is attempted to oscillate the arm 16 and so bring the follower '17 into contact with the lead screw 11i, the projection 34e on the arm 1G will ride upon the outer surface of the rotating notched plate 3Q, until one of the notches 33 is in a position directly under it at which time the arm 16 can be oscillated so that the projection will pass through one of the notches 33 in the plate 32. ln this oscillated position the follower 17 is placed in engagement with the lead screw 14; and the tool 13 is in cutting position relative to the work.

The number of notches 33 in the plate are shown as being four. It will be understood howeverthat this number may be varied Vwith the requirements of the threads being cut.

llfhat I claim is:

1. A screw thread cutting attachment for lathes having a lead screw and an oscillating and axially movable tool controlled by a follower engaging said lead screw, comprising in combination, a-V rotatably mounted member disposed at right angles to said lead screw adapted to be driven therefrom, and spaced means about the periphery of said member to enable the follower to be manually oscillated and engaged with the lead screw when the tool and worlr are in predetermined exact relative positions.

2. A screw thread cut-ting attachment for lathes having a lead screw and an oscillating and axially movable tool controlled by a follower engaging said lead screw, comprising in combination, a member adapted to be rotated in timed relation to said lead screw, a member thereon having a cut-away portion, and a projection on said oscillating follower adapted, when said member is in predetermined positions, to permit oscillation of said follower into engagement with said lead screw.

3. A screw thread cutting attachment for lathes having' a lead sore i and an oscillating and ar-:ially moif'able tool controlled by a follower engaging said lead screw, comprising in combination., a member adaptedto be rotated in .iedrelation to said lead screw, a member thereon having equally spaced cutaway portions, and a projection on said oseillating follower adapted, when said meinber is in predetermined positions, to permit oscillation of said follower into engagement with said lead screw.

4t. A screw thread cutting attachment for lathes having a lead screw and an oscillating and axially movable tool controlled by a follower engaging said lead screw, comprising in combination, a member adapted to be rotated in timed relation to said lead screw, a member thereon having av plurality of equally spaced cut-away portions, and a projection on said oscillating follower adapted, when said member is in predetermined positions, to pass through the cut-away portions of the member and permit oscillation of said follower into engagement with saidA lead screw.

5. A screw thread cutting attachment for lathes hai-'ing a lead screw and an oscillating and axially movable tool controlled by a follower engaging said lead screw, comprising in combination, a member adapted to be rotated at a reduced speed and in timed relation to said lead screw, a member thereon having spaced cut-away portions, and a projection onv said oscillating follower adapted to contact with the face of the omember and when said member is in predetermined positions to permit oscillation of said follower into engagement. with said lead screw.`

6. A screw thread cutting device for lathes comprising in combination, a lead screw adapted to be attached to said lathe and rotated by a work rotating spindle, means to vary the rotation of said lead screw relative to the spindle, an oscillating shaft mounted for axial movement and eX- tendiiig longitudinally of the lathe, a tool supporting carriage mounted thereon and adapted upon oscillation to engage a tool with the work, means also mounted on -said oscillating shaft adapted when the shaft is oscillated toits operative position to engage a follower with the lead screw, and means engaging and rotated by said lead screw lpermitting oscillation of said shaft to engage the toolwith the work in predetermined relative positions only of the lead screw and follower.

7; Ascrew thread cutting device for lathes comprising in combination, a lead screw adapted to be attached to said lathe and Cil rotated by a Work rotating' spindle, means to Vary the rotation o't Said lead screw relative to the spindle, an oscillating Sha't't mounted for axial movement and extending;l longitudinali)v of' the lathe7 a tool Supporting carriage mounted thereon and adapt-ed upon oxcillation to engage a tool with the wort:` moana` also mounted on said oscillating sllatt adapted when thc slt-att is oscillated to its operative position to engage a 'follower with the lead screwl` and a notched plate rotated hy Said lead Screw permittingl` oscillation ot Said Shaft to engage the tool with the work when one of the notches in Said plate is rotated to aiposition in alignment With a projection carried by said follower.

S. A screw thread cutting' device 'tor lathes comprising' in combination, a lead Screw adapted to he attached to Said lathe and rotated by a Work rotating' Spindle, means to vary the rotation oit Said lead screw relatire to the spindle, an oscillating shaft mounted tor axial movement and extending longitudinallj,v of the lathe` a tool supporting 'arriage mounted thereon and adapted upon ocillation to engage a tool with the work. means also mounted on Said o.-:cillatin "y r-hai't adapted when the sha't is oacillated to its operative position to engage a l'ollower with the lead f--icre\\, and a plate. having nett-hes therein rotated hy Said lead screw and permitting` ocillation ot said Shatt to engage the tool with the work in prcdetermincfl relative positionsl oni)v and when one ot said notches ifs' in alignnient with a projection adjacent the tollmver.

In tetiinorqv whereof` l hereto :itlix in); Signature.

HENRY E. DURKICE. 

